1. Field of the Invention
The present invention relates generally to magnetic field applications and antenna arrangements, such as those used in radio frequency identification systems and related identification/recognition fields and, in particular, to an antenna arrangement for providing increased signal recognition and identification properties.
2. Description of the Related Art
In the field of identification and recognition systems and, for example in the field of radio frequency (RFID) identification systems, a system must be provided to allow for the communication between a reader/recognizer and an item, such as a tagged item. The identification is typically accomplished by generating a field, such as a magnetic field, capable of interacting with and communicating with an identification element, such as a tag, positioned on the item. The field can either activate or power the tag, in a passive system, or the tag may include internal power sources to facilitate communications with the system reader/recognizer. The magnetic field is typically generated by applying a current to an antenna, such as an antenna wire and the like. Accordingly, the antenna is powered and emits the field, which is used in identifying object or items within the field.
One drawback in the field and art of tag recognition, such as in the field of inventory systems, is the inability of the reader to identify tags that are positioned in “dead” areas or otherwise oriented in unreadable positions, such as perpendicular to the reader-generated field. Accordingly, there is a need in the art to provide systems with improved identification functionalities, capable of reading a tag, and therefore identifying an item, regardless of item or tag orientation or position within the system or container.
One manner of creating such improved identification characteristics is by the provision of a three-dimensional magnetic pattern. Such prior art systems, however, require complex antenna arrangements in order to produce such a field. For example, see U.S. Pat. No. 6,696,954 to Chung. In particular, these prior art systems require an antenna, positioned on each of the X-, Y- and Z-axis. One drawback to this method and arrangement is that only the tag (transponder) closest to the antennae reader has the maximum energy transfer, and in order to obtain a three-dimensional magnetic field, a cube (X-Y-Z) form is required. For example, in order to identify and read the array of transponders or tags when positioned close together a change in the transponder located by the end of the array is required, which will not otherwise be identified due to low power magnetic field in that position.
According to the prior art, FIG. 1. is a schematic illustration of a known three-dimensional loop antenna, each axis (X-Y-Z) having its own loop antenna. Tags (or transponders A1, A2, A3, B1, B2, B3, C1, C2 and C3 are positioned in this cube or box antenna arrangement, which consists of antennae A, B and C. In operation, when Antenna A is “ON”, it would identify tags A1, A2, A3, and likely C1 and C3. Tag A1 receives maximum energy transfer, followed by tags A2, A3, C1 and C3. If additional “A” tags (e.g., A4, A5, A6, etc.) were positioned on top of tag A3, there remains the possibility that a change in the tag position would not be read, since the tags receive less energy transfer. Similar results would occur with respect to the remaining tags during activation of Antenna A and Antenna B. Accordingly, there remains a need in the art for an antenna arrangement that improves the accuracy and efficiencies of the recognition system.